Safety device for machines



May 8, 1934. M, s GATE 1,958,128

SAFETY DEVICE FOR MACHINES Filed July 8, 1930 5:5 imi@ l Patented May 8,1934 TES Mrap

cargar oFFllcE SAFETY DEVICE FOR Application July 8, 1930, Serial No.466,47@

2 Claims.

This invention relates to safety devices for machines, and is especiallyapplicable to machines which are operated intermittently by means ofmanually actuated clutches; for example, beam presses of the typecommonly used for die-stamping sheet material such as sheet-metal,leather, or rubberized fabric.

The chief object of the invention is to prevent operation of the machinewhile either of the operators hands remains therein. A more specificobject is to provide improved safety mechanism automatically preventingoperation of the machine while the operators hands are therein, andpermitting its operation immediately upon the withdrawal-of his hands.

' Of the accompanying drawing:

Fig. 1 is a front elevation of a beam press embodying my invention inits preferred form, and the work and a. cutting die therein.

Fig. 2 is a detail elevation of the safety device and associatedmechanism of the press.

Fig. 3 is a section on line 3-3 of Fig. 1 showing the position of theoperators hand with relation to the safety mechanism.

Fig. 4 is a view similar to Fig. 3, the operators hand being removed.

Referring to the drawing, represents generally a beam press comprisingan adjustable lower platen 1l, a die-block 12 thereon, adjusting screws13, 13 for raising and lowering said platen, a movable cross-beam orupper platen 14 mounted upon the upper ends of vertically slidable bars15, 15, and a cam-shaft 16 for actuating said upper platen througheccentric cams 50, 50, secured to said shaft just inside the endstandards 17, 17, said cams coacting with pitmans 5l, 51, hinged as at52 to crossbars 53, 53 connecting the lower ends of the bars 15, theconstruction and operation of the parts being well known in the art. TheWork 18 is mounted upon the die-block 12, and 19 is a cutting die uponthe work in position to be struck by the upper platen 14 upon descent ofthe latter. The cam-shaft 16 is provided at one end with a malecone-clutch member 20 which coacts with a shiftable, constantly driven,belt pulley 21 constituting a female cone-clutch member, for rotatingthe cam-shaft 16 to operate the press. The clutch is engaged anddisengaged by a forked shipper-lever 22 which is fulcrumed at 23 on abracket 24 extending from the frame of the press, said lever beingactuated by a push-rod 25 hinged to its upper end and connected througha pair of bell crank levers 26, 26, pivoted on the frame of the machine,and links 27, 27, with a treadle 28. The latter is secured at the rearof the machine to a rock-shaft 29 and is connected to the framework ofthe machine by tension springs 30, 30 which normally hold the treadle inits upper position, with the clutch disengaged. A brake-drum 31 ismounted upon the cam-shaft 16 and coacts with a brake-shoe 32 pivotallymounted upon a bracket 33 extending from the frame of the machine andadapted to be raised against the brake-drum by an arm 34 secured to therock-shaft 29.

Pivotallymounted upon the framework of the machine, opposite the end ofthe push-rod 25 remote from the shipper-lever 22, is a latch or pawl 35adapted alternatively to be raised or lowered to permit or preventlongitudinal movement of the said push-rod, and thereby to control theoperation of the clutch. The pawl 35 is adapted to be raised by means ofa solenoid 36, the movable core 37 of which is connected at one end tothe pawl, and has its opposite end connected by a tension spring 38 toan arm 39 which is part of a bracket 40 by which the solenoid is mountedupon the framework of the machine. The solenoid is energized throughthea/electrical conductors 4l, the arrangement being such that whenelectrical current is flowing through the solenoid its core 37 israised, against the tension of the spring 38, the pawl 35 being therebylifted to the position shown in full lines in Fig. 2, where it presentsno obstruction to the push-rod 25 and free longitudinal movement of thelatter is permitted.

Energizing of the solenoid is eiected automatically, whenever theoperators hands are absent from beneath the upper platen 14, by means oflight-sensitive mechanism, preferablyr of the type employing aphoto-electric tube. The photo-electric tube 42 is mounted upon one ofthe side frames 17 of the machine at the front thereof at an elevationslightly above the dieblock 12, the said tube being enclosed in asuitable housing 43 which is provided with a, hooded window which isdirected toward the opposite side of the machine, the arrangement beingsuch that the tube is shielded from any light other than the sourceintended for the operation of the device. Mounted upon the opposite sideframe 17 of the machine is an electric lamp 44 which preferably isprovided with a. shroud or housing 45, the latter being formed with aprojector, which may include a condenser lens, for directing a beam oflight across the front of the press, toward the photo-electric tube 42.'Ihe light beam is indicated at 56, Fig. 1, and it is so disposed withrelation to the die-block 12 that it is interrupted by the hand, Wrist,or arm of the operator as he manipulates the work 18 upon the die-blockor the die 19 upon the work, substantially as shown in Fig. 3.

Power for operating the photo-electric controlled relay mechanism andfor energizing the solenoid 36 is supplied through conductor wires 46which enter a photo-electric controlled relay unit 47 containing theusual thermionic valve cascade amplifier and relays, this unit and thephoto-electric tube being of well known construction so that a detaildescription of its organization and circuit may be omitted herein. Thephoto-electric tube 42 is connected with the relay unit 47 by conductorWires 48, and the conductors 41 from the solenoid 36 also are connectedwith said relay unit, the arrangement being such that when light fromthe lamp 44 falls upon the photo-electric tube 42, current from thepower conductors 46 flows through the solenoid 36 and actuates thelatter to lift the pawl 35, thus permitting free movement of thepush-rod 25 for manipulating the press clutch. Interruption of the lightbeam 56, as by the operator inserting his hands between the upper andlower platens of the press, causes such diminution of the currentflowing through the tube 42 as to effect the disconnecting of theconductors 41 from the power conductors 46, with the result that thesolenoid is de-energized which permits the spring 38 to retract the core3'7 of the solenoid and thus to move the pawl 35 into the position shownin broken lines in Fig. 2, where it is disposed in the path oflongitudinal movement of the push-rod 25, thus disabling the clutchmechanism.

The improved safety device is automatic and practically instantaneous inits operation, so that it in no way curtails the output of the press. Itis simple in construction and requires no extensive alteration ofexisting structures.

The invention may be modified within the scope of the appended claims asI do not limit the claims wholly to the specific construction shown anddescribed.

I claim:

1. In combination with a press, a clutch, a starting member requiringmanually to be moved in one direction to engage and in the oppositedirection to disengage the clutch, a pawl adapted to be moved intoassociation with the starting member to prevent movement thereof, and asafety device comprising light-sensitive mechanism for so moving saidpawl when the operators hands are in a dangerous position in the press.

2. In apparatus of the character described, the combination of a clutch,a starting member requiring to be moved in one direction to engage andin the opposite direction to disengage the clutch, a pawl adapted to bemoved into the path of the starting member to prevent movement of thelatter, a solenoid adapted to be energized to so move said pawl, andlight-sensitive mechanism controlling the action of the solenoid.

IALCOLM S. CATE.

